People more likely to choose a spouse with similar DNA, research shows

Individuals are more genetically similar to their spouses than they are to randomly selected individuals from the same population, according to a new study from the University of Colorado Boulder.

Scientists already knew that people tend to marry others who have similar characteristics, including religion, age, race, income, body type and education, among others.

In the new study, published in the journal Proceedings of the National Academy of Sciences, scientists show that people also are more likely to pick mates who have similar DNA. While characteristics such as race, body type and even education have genetic components, this is the first study to look at similarities across the entire genome.

"It's well known that people marry folks who are like them," said Benjamin Domingue, lead author of the paper and a research associate at CU-Boulder's Institute of Behavioral Science. "But there's been a question about whether we mate at random with respect to genetics."

For the study, Domingue and his colleagues, including CU-Boulder Associate Professor Jason Boardman, used genomic data collected by the Health and Retirement Study, which is sponsored by the National Institute on Aging.

The researchers examined the genomes of 825 non-Hispanic white American couples. They looked specifically at single-nucleotide polymorphisms, which are places in their DNA that are known to commonly differ among humans.

The researchers found that there were fewer differences in the DNA between married people than between two randomly selected individuals. In all, the researchers estimated genetic similarity between individuals using 1.7 million single-nucleotide polymorphisms in each person's genome.

The researchers compared the magnitude of the genetic similarity between married people to the magnitude of the better-studied phenomenon of people with similar educations marrying, known as educational assortative mating. They found that the preference for a genetically similar spouse, known as genetic assortative mating, is about a third of the strength of educational assortative mating.

The findings could have implications for statistical models now used by scientists to understand genetic differences between human populations because such models often assume random mating.

The study also forms a foundation for future research that could explore whether similar results are found between married people of other races, whether people also choose genetically similar friends, and whether there are instances when people prefer mates whose DNA is actually more different rather than more similar.

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User comments

i read here that people like the body odor of people genetically dissimilar...

"Claus Wedekind and Dustin Penn, in a study conducted for the journal Nephrology Dialysis Transplantation, had 121 men and women rank the pleasantness of six T-shirts (worn by two women and four men). When the "pleasantness" ratings were compared with the degree of genetic similarity between MHC genes, a higher pleasantness rating was correlated with lower genetic similarity."

Well there are several flaws with the study of course . Lets be specific here so every body understands :There is clearly ethnic concentration among individuals of European ancestry in the United States that is captured by geography and regional variability based in ethnicity is well known . And there is no argument that being born in the same ` census division` which is ( Group of neighboring municipalities joined together for the purposes of regional planning and managing common services ) explains some may be most of the preference for intra ethnic marriages in the United States of course nobody will argue against that . Two individuals of both sexes have higher changes to meet each other when they live –long periods of their lives- close proximity to each other .Which means within the same `census division`. Even they are met randomly each other in a completely different location and just learning that they are indeed originating from close geography in their early childhood –emotionally and psychologically bonds them to each other-.When early Immigrants settled in this new land called America they chose to settle near same geography of their earlier settled `countrymen` with same cultural/religious/ethnic /language background `that is fundamental` and historical well established fact of new immigrants to America (Basically an Immigrant Nation ) . In other words American Immigrants are NOT distributed randomly BUT with predetermined geography of previous settlers affected their later settlement too , simply they felt more secure to be close to their countrymen of origin .Genetic wise SNP (Single Nucleotide Polymorphism) has nothing to do with easily recognizable or noticeable `outside looks``Phenotype ` of any individual so two individual can not determine that genetic similarity no matter how you slice it . BUT they can easily determine `each other`s ethnicity and background` and original country of their ancestors and naturally socially they `feel more secure with each other BECAUSE of similar ethnicity and ancestral relationship , exactly the same way their immigrant ancestors felt the same way when they settled America . Trust is the key word in any marriage relationship of course , and ever polarized multiethnic and multiracial characteristics of Immigrant America obviously pushes individuals to find `Trust` in their own `ethnicity` and `country of origin` that is very natural obviously .Being from same ` emigrant country of origin` ITSELF increases the probability of SHARED SNP (Single Nucleotide Polymorphism) of their DNA rather than they could ever –SNIFF OUT or VISUALLY DIFFERENTIATE - similar SNP or `Genetically similar Alleles ` ... Genome wide `GCTA` DNA base pair analysis done at this study is NOTHING but the conformation of being from the same or similar country of origin –emigrant ethnicity – ... Mutual Trust in marriage (what builds trust ? ) and Geographic proximity (opportunity )to meet each other are key important components (variables) here ...So the bottom line is : A- Immigrant population of America is NOT ideal for this type of study to determine or conclude that same/similar DNA attract each other and to marry to each other as they claim – US white population is NOT `randomly distributed geographically yet ` -as far as original white Immigrants concerned , they are distributed `Mosaic` like `census divisions` and geographic pattern of settlements all along from the start ; SO the chance of two individuals finding a mate obviously HIGHER at the same GEOGRAPHY or PROXIMITY to each other within the same Census Division . THAT clearly means –SIMILAR GENETIC SNP polymorphism at the same geography because of similar ancestral relationship of original homeland prior to migration to America - B- The `homogeneously ` populated countries are more proper – statistically speaking- for the `GENETIC KINSHIP` vs. `MARRIAGE` correlation studies to have more accurate conclusion and correlation .C- Evolutionary wise Inbreeding and Close Kinship and their off springs are simply `doomed in the long run` due to increased `genetic malformations` and `genetic diseases` so it is simply illogical and absurd to assume that the mother nature choses `inbreeding` or `genetically close individual`s mating` rather than preferentially choosing `GENETICALLY DIFFERENT INDIVIDUALS` for the purpose of increasing `VARIABILITY` for the survival of the species as well as the well being of the off springs .http://www.pnas.o...1426111. .pdf (Supplement of the Study)